A large variety of additives for improving various properties in hydrocarbon oil compositions are well known, and in fact a large number of these compositions are being used on a commercial level. The various additives are used for a variety of purposes, some of which relate to improving the low temperature (i.e., less than about 30.degree. F.) flow properties of various types of hydrocarbon oils, including both lubricating oil fractions and other oil fractions including heating oils, diesel oils, middle distillates, and the like, and others of which relate to improving the oxidation stability of these various types of hydrocarbon oils. These flow improvers generally modify the wax crystals in both lubricating oils and other hydrocarbon fractions and crudes so as to impart low temperature handling, pumpability, and/or vehicle operability thereto. These parameters are generally measured by a variety of tests, including pour point, cloud point, mini-rotary viscometry (MRV) and others. Those other additives are used primarily for imparting anti-oxidant properties to these hydrocarbon fractions, including lubricating oil fractions.
Cloud point (ASTM D 2500) is the temperature at which wax crystals first appear as a haze in a hydrocarbon oil upon cooling. Such wax crystals typically have the highest molecular weight of the waxes in the hydrocarbon oil and therefore the lowest solubility. The cloud point of a hydrocarbon oil reflects the temperature at which problems in filtering the oil are encountered. However, the cloud point of a lubricating oil (as opposed to a fuel oil) is of less significance than is its pour point because the filters typically encountered by a lubricating oil (e.g., combustion engine oil filters) have a relatively large pore size, and filter plugging is therefore less of a problem in these environments.
Pour point is the lowest temperature at which a hydrocarbon oil will pour or flow when chilled, without disturbance, under specified conditions. Pour point problems arise through the formation of solid or semi-solid waxy particles in a hydrocarbon oil composition under chilled conditions. Thus, as the temperature of the oil is decreased, the distribution of such oil by pumping or siphoning is rendered difficult or impossible when the temperature of this oil is around or below the pour point of the oil. Consequently, when the flow of oil cannot be maintained, equipment can fail to operate.
It has therefore been necessary to develop various additives for the purpose of influencing the cold temperature flow properties of hydrocarbon oils.
The general term "lubricating oil flow improver" (LOFI) covers all those additives which modify the size, number, and growth of wax crystals in lube oils in such a way as to impart improved low temperature handling, pumpability, and/or vehicle operability as measured by such tests as pour point, cloud point, and mini rotary viscometry (MRV). The majority of lubricating oil flow improvers are polymers or contain polymers. These polymers are generally of two types, either backbone or sidechain.
The backbone variety, such as the ethylene-vinyl acetates (EVA), have various lengths of methylene segments randomly distributed in the backbone of the polymer, which associate or cocrystallize with the wax crystals inhibiting further crystal growth due to branches and noncrystallizable segments in the polymer.
The sidechain-type polymers, which are the predominant variety used as LOFIs, have methylene segments as the side chains, preferably as straight side chains. These polymers work similarly to the backbone type except the side chains have been found more effective in treating isoparaffins as well as n-paraffins found in lube oils. More specifically, LOFIs are typically derived from unsaturated carboxylic acids or anhydrides which are esterified to provide pendent ester groups derived from a mixture of alcohols. Most current commercial additives of this type thus require the use of relatively expensive alcohols for their production. Representative examples of this type of side chain LOFI include dialkyl fumarate/vinyl acetate copolymers and esterified styrene/maleic anhydride copolymers.
It would be extremely advantageous if additives could be developed which rely on less expensive olefins rather than alcohols in the synthesis of low temperature flow improvers without sacrificing the properties of conventional alcohol-based LOFIs. Several commercially unsuccessful attempts have been made in the past using alkylated phenol formaldehyde condensates.
One additive composition which has been disclosed as a pour depressant for fuels and crude oils is set forth in British Patent No. 1,173,975. The additive disclosed in this patent is a phenol-aldehyde (preferably formaldehyde) polymer in which the phenol has an R - or RCO - substituent in which R is hydrocarbyl or substituted hydrocarbyl. R is further said to contain from 18 to 30 carbon atoms, and is preferably a straight chain alkyl group. The specific examples in this patent which use olefins to provide these R groups include various internal olefins, and there is no specific disclosure regarding the advantages of using terminal olefins therein. Another patent, British Patent No. 1,167,427, discloses the use of esters of such phenolaldehyde polymers for pour point reduction of fuel oils. In both of these British patents, the oils to be treated are said to have a maximum viscosity of about 1500 cSt at 100.degree. F., and neither recognizes the significance of utilizing specific alpha-olefins and mixtures thereof to produce these condensation products, or the advantages of imparting essential linearity to the olefin derived side chains.
Another class of such additives are essentially known as anti-oxidants or oxidation stabilizers. It is thus known that a number of phenolic and sulfur-containing compounds possess anti-oxidant properties in connection with various organic materials which are subject to oxidative decomposition in the presence of air, oxygen or ozone. These include, for example, U.S. Pat. No. 3,060,121. In this patent compounds have the general formula ##STR1## in which R, in its broadest sense, contains from 1 to 22 carbon atoms, R.sub.1 and R.sub.2 are up to 3 carbon atoms, A1 is up to 10 carbon atoms, x can be 3, and the maximum molecular weight under these conditions would thus be 1,346. These compounds are disclosed as anti-oxidants for certain organic materials. However, the compounds disclosed in this patent have relatively low molecular weights, again generally not more than about 1,350 as set forth above.
U.S. Pat. No. 3,986,981 discloses yet another class of anti-oxidants in this case comprising bis-phenolic polymers in which the repeating units can include compounds of the formula ##STR2## in which the R.sub.2-4 radicals can comprise alkyl groups of from 1 to 8 carbon atoms, connected by sulfur methylene or butylidene bridging groups. Again, however, the compounds in question are of relatively low molecular weights.
Similarly, U.S. Pat. No. 3,951,830 discloses lubricant additives particularly useful as oxidation inhibitors comprising sulfur and methylene-bridged polyphenol compositions which are produced from reacting phenol with formaldehyde and subsequently sulfurizing the methylene-bridged intermediate, or as an alternative sulfurizing the phenol and then reacting same with formaldehyde. The product of same is believed to be a sulfur and methylene-bridged polyphenol composition, in which the phenol can be substituted with aliphatic or cycloaliphatic radicals of at least 6 carbon atoms and up to as many as 7,000 carbon atoms. However, all the examples in this patent use branched olefins such as polyisobutylene substituted phenols therein.
U.S. Pat. No. 4,446,039 discloses yet another additive for fuels and lubricants which, in this case, is prepared by reacting aromatic compounds, such as phenol or substituted phenol including alkyl groups of at least 50 carbon atoms, with an aldehyde, such as formaldehyde, and a non-amino hydrogen, active hydrogen compound, such as phenol, optionally along with an aliphatic alkylating agent of at least 30 carbon atoms. This patent also discloses that sulfurized additive compositions thereof can also be used as lubricant additives and fuel oil additives. It does not disclose the use of alpha-olefins of less than 50 carbon atoms for the alkylation of phenol.
Another additive for improving the various cold flow characteristics of hydrocarbon fuel compositions is in U.S. Pat. No. 4,564,460. In this patent the additives are broadly disclosed as including either an oil soluble ethylene backbone polymer or various hydrocarbyl-substituted phenols as a first component and various reaction products of hydrocarbyl-substituted carboxylic acylating agents and amines and/or alcohols. The hydrocarbyl-substituted phenol constituents of this overall additive are also broadly described, and they can include repeating aromatic moieties, such as those shown in column 14 thereof, in which the R* groups include substantially saturated monovalent hydrocarbon-based polymers of at least about 30 aliphatic carbon atoms or hydrocarbyl groups of from 8 to 30 carbon atoms. These, in turn, can be provided by internal olefins or alpha-olefins, and can be either straight or branched. Furthermore, at column 14, lines 1-40 of the patent the phenol compounds are disclosed as including various bridging compounds, including -S- (line 36). Notwithstanding the extremely broad disclosure of this patent, not a single working example is provided therein which makes or tests any hydrocarbyl substituted phenol or aldehyde condensation product thereof.
British Patent No. 2,062,672 discloses another such additive, in this case including a sulfurized alkyl phenol and a carboxylic dispersant. The alkyl phenols disclosed in this patent can include alkyl radicals of up to 1000 carbon atoms, but the disclosure also mentions the use of methylene-bridged alkyl phenols prepared by the reaction of the alkyl phenol and formaldehyde.
Canadian Patent No. 1,192,539 discloses yet another alkyl-phenol-containing lubricant additive. In this case the lubricant is designed for two-cycle engines and the phenolic compound includes a hydrocarbyl group of an average of at least ten aliphatic carbon atoms, and preferably containing at least 30 and up to 400 aliphatic carbon atoms (page 11, lines 13-17). Furthermore, the disclosure states that the aromatic ring can be a linked polynuclear aromatic moiety, which can also include other substituents, and which can be linked by a number of groups, including sulfide linkages (page 6, lines 1-8). Once again in this case the disclosure is very broad, and includes innumerable variations on the alkyl phenol component.
There are also a number of patents which disclose other alkyl phenol polysulfides, primarily di-sulfides, as additives to mineral oils to improve properties including high temperature stability thereof. These include U.S. Pat. No. 2,174,248 which teaches the use of alkyl phenols produced from olefins of from 2 to 8 carbon atoms with the sulfur compound to produce the di-sulfide. Also, U.S. Pat. Nos. 2,198,828 and 2,209,463 have similar disclosures in this regard.
British Patent No. 2,062,672 discloses another such additive, in this case including a sulfurized alkyl phenol and a carboxylic dispersant. The alkyl phenols disclosed in this patent can include alkyl radicals of up to 100 carbon atoms, but the disclosure also mentions the use of methylene-bridged or sulfur bridged alkyl phenols prepared by the reaction of the alkyl phenol and formaldehyde or a sulfurizing agent.
U.S. Pat. No. 3,629,225 also discloses sulfurized alkyl phenols of limited size (up to three repeating units), and U.S. Pat. No. 4,305,832 discloses a sulfurized phenol composition as set forth in column 1 thereof in which the phenols include an alkyl group having from 1 to 18 carbon atoms, and the overall compositions again have a limited molecular weight with up to four repeating units therein.
Irrespective of all of the above, and the large number of additive compositions which have previously been proposed and utilized for altering both the flow properties and the oxidative stability of hydrocarbon oils and lubricating oil compositions, the search has continued for additional additive compositions which can improve both the flow characteristics and the oxidative stability of these various hydrocarbon compositions, and which can also be easily produced on an economical basis.
Commonly assigned U.S. Pat. Nos. 5,039,437 and 4,976,882, both filed on Oct. 8, 1987 by some of the same inventors herein are directed to alkyl phenol-aldehyde condensates and sulfur bridged alkyl phenols condensates respectively and are incorporated herein by references.